# Show the differences between the internal logs of `self` and `expected`.
	#
	# If there is no differences, return an empty string. Else, return a string
	# designed to be printed in the terminal. In this case, `=` means “in both”,
	# `<` means “in `self`” and `>` means “in `expected`”.
	fun diff(expected: SAXEventLogger): Text do
		var buf = new FlatBuffer
		var sub_diff: Array[Int]
		var equal: Bool
		var i = 0
		var min: Int
		var max: Int

		if log.length < expected.log.length then
			equal = false
			min = log.length
			max = expected.log.length
		else if expected.log.length < log.length then
			equal = false
			min = expected.log.length
			max = log.length
		else
			equal = true
			min = log.length
			max = log.length
		end

		while i < min do
			sub_diff = diff_entry(log[i], expected.log[i])
			if sub_diff.length > 0 then
				if equal then
					diff_append_matches(buf, log, [0..i[)
					equal = false
				end
				diff_append_deletion(buf, log, i, sub_diff)
				diff_append_insertion(buf, expected.log, i, sub_diff)
			else if not equal then
				diff_append_matches(buf, log, [i..i])
			end
			i += 1
		end
		if log.length < expected.log.length then
			while i < max do
				diff_append_insertion(buf, expected.log, i,
						[0..(expected.log[i].length)[)
				i += 1
			end
		else
			while i < max do
				diff_append_deletion(buf, log, i, [0..(log[i].length)[)
				i += 1
			end
		end
		return buf
	end